LLVM purges loads from `nullptr` in functions not marked with
`null_pointer_is_valid`. This can lead to uninitialized accesses to tiny
code variables, which in turn lead to cross-`TranslationBlock` phis
which can prevent argumentless outlining.
Adding to the `root` function the `null_pointer_is_valid` attribute
fixes this problem.
This commit drops libptc in favor of its new form libtcg.
It brings several improvements, among which:
* The QEMU version we work on has been upgraded.
* CPUStateAccessAnalysis has been reimplemented in a way that makes it
easier to debug and solves some limitations (e.g., tracking leaking
pointers).
* Identification of pieces of the CPU state that are read by each helper
and fixing access to the CPU state is now performed at build-time.
* We no longer mmap the code we need to translate, dropping all the
issues related to code that needed to be mapped where something is
already present.
* We now have two distinct flavors of helper modules: the full one and
the "slim" one. The latter contains the definition only of functions
we intend to inline. It is used in most of the pipeline, a good thing
since we spend less time optimizing code we don't really care about.
The full module is only used on the re-compilation branch of the
pipeline.
* We no longer split the `cpu_loop` function.
* We change MetaAddress to rely on architectures from `model::` as
opposed to the LLVM ones.
* We no longer attach debug info to LLVM IR containing the original
assembly.
* We now verify that the lifted code only contains code we expect.
* Make the following private headers public:
* Lift/CPUStateAccessAnalysisPass.h
* Lift/CSVOffsets.h
* Lift/PTCDump.h
* Lift/VariableManager.h
* Move from revngSupport to revngLift:
* IRAnnotators.{h,cpp}
* SelfReferencingDbgAnnotationWriter.{h,cpp}
* Move from revngSupport to revngModel:
* FunctionTags.{h,cpp}
* ProgramCounterHandler.{h,cpp}
* Move from revngSupport to revngRecompile:
* OriginalAssemblyAnnotationWriter.{h,cpp}
Before this commit, `forceEmptyMetadata` did not return a bool to notify
when it changed something.
This in turn caused the pass to return the wrong value when the only
change applied was to force the empty metadata.
This commit fixes the issue, letting `forceEmptyMetadata` return a bool,
and propagating that until where it matters.
This commit is the final step in ensuring all the pipes commit what they
should. It also asserts this actually happens, enabling us to easily
catch future problems.
Giacomo Vercesi